This invention relates to apparatus for guiding portable power saws along a predetermined cutting path. More specifically, apparatus which provides guide assembly which can accommodate most power circular saws for cutting and trimming doors and other workpieces made of plywood, veneer, and particle board such as masonite.
The invention of portable power saws effected a revolution in carpentry and the building trades. On-site work could be conveniently done without having to drag a bulky table saw to the work site. Portable power saws are relatively inexpensive, are easily secured and stored when not in use, and take up little room.
Portable power saws have shortcomings, foremost in their inability to make accurate long cuts in plywood, particle board or lumber of sizeable length. Saw guides have been devised to solve this problem, as exemplified in U.S. Pat. Nos. 3,874,261, Murray; 4,028,976, Kundikoff; 3,983,776 and 4,050,340 Flanders; 4,059,038 Rietema, 4,075,920, Neal; 4,095,632 Raulinaitis; and others. These guides work well for the purpose of a simple saw guide but there is a problem of the tendency to chip and splinter along the saw kerf when working with particle board and especially veneer. This problem is especially acute when a carpenter has to trim doors and materials with finished surfaces as veneers on both sides, which is not solved by the splinter reducing method of placing the single veneer side down. When working with materials having double veneered sides such as doors, the circular blade cuts in an upward motion and splinters the upper veneer surface along the kerf.
One solution devised for this problem is to use a twin bladed scribing device to score two parallel lines on the workpiece which form the outer limits of the kerf of the intended cut. This feature may be seen in the device sold under the trade name "Guide 'N Scribe" made by Penn Scarf Mfg. Co. This method entails an extra separate step in the cutting procedure. A more practical solution is incidentally mentioned in U.S. Pat. No. 4,075,920, Neal. That patent discloses two guides, one for the baseplate edge of the saw farthest from the saw blade, and another edge guide contiguous with the blade itself.
Close contact of a portion of the Neal saw guide to the workpiece prevents splintering by providing support to the wood that is cut.
But the Neal device has several serious drawbacks that become evident during use. The "Guide plate" of the Neal invention must be cut to size by the saw. This operation is performed so that the saw baseplate rests snugly between the inner guide edge and the guide edge. Once this cut is made, in contrast to the present invention, further adjusting cuts of the guide edge are difficult or impossible because the severable portion is not wide and is secured to the rest of the "Guide plate" by a tongue and groove joint. Renewable guide edges will be required when different saws with differing baseplate widths are used and also when the set of the saw blade wears down. Blunting of the saw teeth is common due to hidden metal fasteners frequently found under the veneer of doors, and also by the inevitable wearing of saw teeth through use.
The present invention also provides a more convenient clamping device for multiple jobs.